This invention relates to a method of purification of waste water by treatment in a granular filter bed that has been activated by bacteria, preferably heterotrophic bacteria.
It is known in the art to remove nitrogen and phosphor simultaneously from wastewater with the use of an active sludge that contains aerobic bacteria. It is also known from the Swedish patent No 456 990 to add the sludge in anaerobic conditions, so that the aerobic bacteria are urged to liberate phosphor, which the anaerobic bacteria can then take up. The process takes place in treatment basins under heavy agitation.
It is known from the French patent No 2619 804 to denitrify drinking water using a granular filter bed, to which are added sources of phosphor and carbon. Here, the majority of the phosphor is taken up by anaerobic bacteria.